Best way to save life is to just use the phone/device less. That's why you're seeing the drop because it's a shiny new beta and we keep poking the device combing through the new features. It's basically the same battery life, no improvements with a slight decrease due to less optimization because it's a beta.
I can disagree here.
I know a lot of people will lose battery quicker from toying with the new iOS, but I have been deliberately checking the battery drain while the phone is not in use, with no apps open in the background and can say I am experiencing much faster battery drain then on 4.3.3.
I'm not really too angry about it, as I HAD to have iOS5 now (I'm not a dev), but for me there is a notable extra loss of battery on iOS 5.
I will continue comparing to iOS 4.3.3 to make sure I'm right.